Locally reinforced hollow structural assembly

ABSTRACT

A reinforced structural assembly is provided including a hollow structure having a cavity with a hole. A bag is inserted into the cavity and has an end with an opening extending out of the cavity through the hole. A device injects a structural foam into the bag. The bag is closed and the end of the bag is inserted into the cavity. A cap is installed over the hole. The foam expands to fill the cavity but is contained within the bag thereby providing localized reinforcement in the desired area.

The application is a continuation of U.S. patent application Ser. No.10/649,975, which was filed Aug. 26, 2003, which claimed priority toU.S. Provisional Application No. 60/430,477, which was filed on Dec. 2,2002.

BACKGROUND OF THE INVENTION

This invention relates to reinforcement of a hollow structure, and moreparticularly, the invention relates to reinforcing a hollow structurewith a material such as a structural foam.

Hollow structural members are used in a variety of vehicle applications.For example, portions of a vehicle body such as A- and B-pillars areformed from thin-walled hollow members. Also, suspension assemblies areincorporating increasingly thinner walls for tubular members such asaxles. Utilizing thin walled structural members has the advantage ofreducing the cost and weight of the assembly incorporating thestructure.

In the case of axles, it is desirable to provide a wall thickness thatmaximizes bending and torsional stiffness while minimizing the weight.However, the thinner the wall thickness, the more susceptible thestructure is to buckling under load. For example, auxiliary hardwaresuch as spring brackets are typically clamped to the hollow axlestructure. The wall may buckle under the clamping load or the leafspring may walk during operation of the suspension assembly. To thisend, prior art axle assemblies have added local stiffeners by welding onadditional reinforcement plates to increase the stiffness, for example.

For vehicle applications with hollow body structures, such as A- andB-pillars for example, structural foams have been injected into thehollow cavity of the structure to provide localized reinforcement. Thestructural foam expands to fill the space and hardens to stiffen thearea. However, walls must be formed in the hollow structure to containthe foam to the desired area since the structural foam is very costly.This is accomplished by stamping or welding steel walls into thestructure to contain the foam. This raises complications in forming thehollow structural member, which can add significant cost whenformulating a design to accommodate the walls for containing thestructural foam.

Therefore, what is needed is a method and apparatus for providing localreinforcement of a hollow structural member while reducing the cost anddesign complexity of prior art solutions.

SUMMARY OF THE INVENTION AND ADVANTAGES

A reinforced structural assembly includes a hollow structure thatdefines a cavity that receives a bag. The bag is filled with a material,and the material is expanded to provide a localized reinforcement areawithin the hollow structure.

In one example, the reinforced structural assembly includes a hollowstructure having a cavity with a hole. A bag is inserted into the cavityusing a tube. The bag has an end with an opening extending out of thecavity through the hole. A device injects a structural foam, such as atwo-part epoxy for example, into the bag. The bag is closed and the endof the bag is inserted into the cavity. A cap is installed over thehole. The foam expands to fill the cavity but is contained within thebag thereby providing localized reinforcement in the desired area. Foraxles, the cap may include a locating feature for positioning acomponent such as a leaf spring.

Accordingly, the present invention provides a method and apparatus forproviding local reinforcement of a hollow structural member whilereducing the cost and design complexity of prior art solutions.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention can be understood by referenceto the following detailed description when considered in connection withthe accompanying drawings wherein:

FIG. 1A depicts a bag being inserted into a cavity of a hollowstructure;

FIG. 1B depicts a bag being injected with structural foam;

FIG. 1C depicts the bag filled with a structural foam;

FIG. 1D depicts the bag closed with an end of the bag having an openinginserted into the cavity;

FIG. 1E depicts the hole of the hollow structure closed with a cap;

FIG. 1F depicts the structural foam fully expanded within the cavity;and

FIG. 2 depicts a suspension assembly with a hollow axle having localizedreinforcement in the area of the suspension attachment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1A-1F, a reinforced structural assembly of thepresent invention is shown at 10. The assembly 10 includes a hollowstructure 12 defining a cavity 14 with a hole 15 in the wall of thestructure 12 providing access to the cavity 14. A bag 16 is insertedinto the cavity 14 through the hole 15 using a tube 17, shown in FIG.1A. The bag 16 includes an end 18 having an opening 20 extending throughthe hole 15. For example, the bag 16 may be rolled up and inserted intoa cardboard tube and then pushed into the cavity 14. The bag may be madeof any suitable material in one example the bag is made of a hightemperature thermoplastic that can withstand the exothermic reaction ofthe expanding foam. Such suitable materials may include a mylar, rubber,or polysulphone. Of course, any number of suitable materials may beused. The bag 16 contains the foam during expansion so that internalwalls or baffles are not required in the hollow structure, which aredifficult and expensive to design and manufacture.

A device 22 having a nozzle 24 injects a foam 26 into the bag 16 throughthe opening 20, as is best shown in FIGS. 1A and 1B. The device 22 maybe manually or automatically operated. The structural foam fillermaterial could be any suitable material having a high modulus. The foam26 may be a composite material such as a glue, a filled acetal epoxy, apolyester, or any other suitable material. One such material isavailable by Henkel under the trade name TEROCORE 1015A and B. TEROCOREis a two component structural foam comprising a high strength expandingtwo-part epoxy with a 2:1 by volume mixed ratio. The TEROCORE epoxyexpands approximately 30% and has a high modulus. TEROCORE is anexothermic material that cures an ambient temperature as the twocomponents are mixed together and cures or hardens 90% within the firstthirty minutes from the inside out. TEROCORE is fully cured within 24hours and is a non-isocyanate material that does not require specialventilation during its use. The epoxy resin portion of TEROCORE has goodstability and determines the curing speed. Fillers may be added to thematerial to improve the mechanical properties, provide saggingresistance, hardness, and determine the compression modules. The curingagent portion of TEROCORE determines the reactivity, adhesion,compression modulus, and shelf life of the material. The expanding agentof TEROCORE dictates the cell structure and reduces the overall weightof the structural foam.

Referring to FIG. 1D, once the structural foam 26 has been injected intothe bag 16, the bag is closed. For example, the end 18 may be twisted,shown at 28, and inserted into the cavity 14. The hole 15 may be closedoff by inserting a cap 30, as shown in FIG. 1E. The cap 30 furthercontains the structural foam 26 during expansion and provides anaesthetically pleasing appearance. The structural foam 26 expands intoengagement with the interior walls of the cavity 14 while remainingcontained in the other directions by the bag 16, as best shown in FIG.1F.

The reinforced structural assembly 10 may be used in any thin walledhollow structural application in need of localized reinforcement. Forexample, the present invention may be used to locally reinforce hollowportions of the vehicle body such as A and B pillars. Specific areas ofthe body may be stiffened enabling thinner walls to be used elsewhere.

The present invention is also suitable for use in suspension assemblies32, as shown in FIG. 2. The suspension assembly 32 includes a hollowaxle 33 for supporting suspension components such as a leaf spring 38. Aportion of the axle 33 may be locally reinforced as described aboverelative to FIGS. 1A-1F to provide additional structural stiffness. Thehole 15 may be closed by a cap 34 having a locating feature 35 such as aprotrusion extending therefrom. A bracket 36 supporting the leaf spring38 may have a feature complimentary to that of the locating feature 35on the cap 34 to locate the suspension assembly 32 relative to the axle33 during assembly. The bracket 36 is secured to the axle 33 by a U-boltassembly 40, as is well known in the art. One of ordinary skill in theart will appreciate that components other than the leaf spring 38described above may be secured to the hollow axle 33 or any other hollowmember. For example, an air spring or any other component that typicallyexerts a large load on the axle 33 may be placed in the reinforced area.In the case of an axle, the hollow axle 33 is typically subject tobuckling under the clamping load or walking of the suspension assembly32 relative to the axle. With the locally reinforced hollow structure,increased stiffness is provided thereby avoiding buckling or walking ofthe suspension assembly.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology that has been used is intended to bein the nature of words of description rather than of limitation.Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

1. A method of locally reinforcing a hollow structure to support acomponent comprising the steps of: (a) inserting a bag into a cavity ofa structure; (b) filling the bag with a material; (c) expanding thematerial to provide a localized reinforcement area within the structure;and (d) supporting a component on the structure at the localizedreinforcement area.
 2. The method according to claim 1, wherein thematerial is a structural foam.
 3. The method according to claim 1,wherein the bag is closed prior to step (c).
 4. The method according toclaim 1, wherein an end of the bag is closed and inserted into thecavity after step (b) and prior to step (c).
 5. The method according toclaim 1, wherein step (a) includes inserting the bag through a hole inthe structure and including installing a cap into the hole subsequent tostep (b).
 6. The method according to claim 5, wherein step (d) includespositioning the component to at least partially overlap the hole.
 7. Themethod according to claim 5, including providing the cap with a firstlocating feature, and providing the component with a second locatingfeature wherein the first and second locating features cooperate tolocate the component relative to the structure.
 8. The method accordingto claim 7, wherein the structure comprises a hollow axle and thecomponent comprises a suspension component.
 9. A method of locallyreinforcing a hollow structure to support a component comprising thesteps of: (a) inserting a bag through a hole in a hollow structure thatdefines a cavity; (b) filling the bag with a structural foam; (c)installing a cap in the hole; and (d) expanding the structural foam toprovide a localized reinforcement area within the hollow structure. 10.The method according to claim 9, wherein step (b) includes closing anend of the bag and inserting the bag into the cavity through the hole,performing step (c) subsequent to step (b), and performing step (d)subsequent to step (c).
 11. The method according to claim 9, includingsupporting a component on the hollow structure at the localizedreinforcement area.
 12. The method according to claim 11, includingproviding the cap with a first locating feature, and providing thecomponent with a second locating feature wherein the first and secondlocating features cooperate to locate the component relative to thestructure.
 13. The method according to claim 11, wherein the hollowstructure comprises a hollow axle and wherein the component comprises asuspension component.
 14. A reinforced structural member comprising: astructure having a cavity, said structure including a hole incommunication with said cavity; a bag insertable through said hole anddisposed within said cavity, said bag defining a space; a structuralfoam disposed within said bag and filling said space to provide alocalized reinforcement area in said structure; and a cap that coverssaid hole.
 15. The reinforced structural member according to claim 14wherein said bag includes an end having an opening that facilitatesinsertion of said structural foam into said bag, said end being disposedwithin said cavity when said cap covers said hole.
 16. The reinforcedstructural member according to claim 14, including a component mountedon said structure at said localized reinforcement area.
 17. Thereinforced structural member according to claim 16, wherein saidcomponent at least partially overlaps said hole.
 18. The reinforcedstructural member according to claim 16, wherein said cap includes afirst locating feature and said component includes a second locatingfeature that cooperates with said first locating feature to positionsaid component relative to said structure.
 19. The reinforced structuralmember according to claim 18, wherein said component comprises asuspension component and said structure comprises a hollow axle.